Atrial natriuretic peptide-initiated cGMP pathways regulate vasodilator-stimulated phosphoprotein phosphorylation and angiogenesis in vascular endothelium

Soluble guanylyl cyclase: A novel target for the treatment of vascular cognitive impairment?

Vascular cognitive impairment (VCI) describes neurodegenerative disorders characterized by a vascular component. Pathologically, it involves decreased cerebral blood flow (CBF), white matter lesions, endothelial dysfunction, and blood-brain barrier (BBB) impairments. Molecularly, oxidative stress and inflammation are two of the major underlying mechanisms. Nitric oxide (NO) physiologically stimulates soluble guanylate cyclase (sGC) to induce cGMP production. However, under pathological conditions, NO seems to be at the basis of oxidative stress and inflammation, leading to a decrease in sGC activity and expression. The native form of sGC needs a ferrous heme group bound in order to be sensitive to NO (Fe(II)sGC). Oxidation of sGC leads to the conversion of ferrous to ferric heme (Fe(III)sGC) and even heme-loss (apo-sGC). Both Fe(III)sGC and apo-sGC are insensitive to NO, and the enzyme is therefore inactive. sGC activity can be enhanced either by targeting the NO-sensitive native sGC (Fe(II)sGC), or the inactive, oxidized sGC (Fe(III)sGC) and the heme-free apo-sGC. For this purpose, sGC stimulators acting on Fe(II)sGC and sGC activators acting on Fe(III)sGC/apo-sGC have been developed. These sGC agonists have shown their efficacy in cardiovascular diseases by restoring the physiological and protective functions of the NO-sGC-cGMP pathway, including the reduction of oxidative stress and inflammation, and improvement of vascular functioning. Yet, only very little research has been performed within the cerebrovascular system and VCI pathology when focusing on sGC modulation and its potential protective mechanisms on vascular and neural function. Therefore, within this review, the potential of sGC as a target for treating VCI is highlighted.

Cardiovascular Functions of Ena/VASP Proteins: Past, Present and Beyond

Actin binding proteins are of crucial importance for the spatiotemporal regulation of actin cytoskeletal dynamics, thereby mediating a tremendous range of cellular processes. Since their initial discovery more than 30 years ago, the enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) family has evolved as one of the most fascinating and versatile family of actin regulating proteins. The proteins directly enhance actin filament assembly, but they also organize higher order actin networks and link kinase signaling pathways to actin filament assembly. Thereby, Ena/VASP proteins regulate dynamic cellular processes ranging from membrane protrusions and trafficking, and cell-cell and cell-matrix adhesions, to the generation of mechanical tension and contractile force. Important insights have been gained into the physiological functions of Ena/VASP proteins in platelets, leukocytes, endothelial cells, smooth muscle cells and cardiomyocytes. In this review, we summarize the unique and redundant functions of Ena/VASP proteins in cardiovascular cells and discuss the underlying molecular mechanisms.

ANP promotes HTR-8/SVneo cell invasion by upregulating protein kinase N 3 via autophagy inhibition

Preeclampsia is a gestational disease characterized by two major pathological changes-shallow trophoblast invasion and impaired spiral artery remodeling. Atrial natriuretic peptide (ANP) is a kind of peptide hormone that regulates blood pressure, while the lack of active ANP participates in preeclampsia pathogenesis. However, the underlying mechanism of how ANP modulates trophoblasts function remains unclarified. Here, we performed isobaric tags for relative and absolute quantification (iTRAQ) in ANP-treated HTR-8/SVneo cells and identified Protein Kinase 3 (PKN3) as the downstream factor of ANP, which was downregulated in preeclamptic placenta. Chromatin immunoprecipitation analysis and luciferase assays showed that NFYA was one of the transcription factors for the PKN3 promoter, which was also regulated by ANP treatment in HTR-8/SVneo cells. Transmission electron microscopy and Western Blotting in HTR-8/SVneo cells indicated that ANP inhibited autophagy via AMPK-mTORC1 signaling, while excess autophagy was observed in preeclamptic placenta. The increased expression of PKN3 and enhanced cell invasion ability in HTR-8/SVneo cells induced by ANP could be abolished by autophagy activation or transfection with PKN3 shRNA or NFYA shRNA or NPR-A shRNA via regulating the invasion-related genes and the epithelial mesenchymal transition molecules. Our results demonstrated that ANP could enhance trophoblast invasion by upregulating PKN3 via NFYA promotion through autophagy inhibition in an AMPK/mTORC1 signaling-dependent manner.

The Vasculature in Pulmonary Fibrosis

Purpose of Review

The current paradigm of idiopathic pulmonary fibrosis (IPF) pathogenesis involves recurrent injury to a sensitive alveolar epithelium followed by impaired repair responses marked by fibroblast activation and deposition of extracellular matrix. Multiple cell types are involved in this response with potential roles suggested by advances in single-cell RNA sequencing and lung developmental biology. Notably, recent work has better characterized the cell types present in the pulmonary endothelium and identified vascular changes in patients with IPF.

Recent Findings

Lung tissue from patients with IPF has been examined at single-cell resolution, revealing reductions in lung capillary cells and expansion of a population of vascular cells expressing markers associated with bronchial endothelium. In addition, pre-clinical models have demonstrated a fundamental role for aging and vascular permeability in the development of pulmonary fibrosis.

Summary

Mounting evidence suggests that the endothelium undergoes changes in the context of fibrosis, and these changes may contribute to the development and/or progression of pulmonary fibrosis. Additional studies will be needed to further define the functional role of these vascular changes.

Neuroendocrine pathways at risk? Simvastatin induces inter and transgenerational disruption in the keystone amphipod Gammarus locusta

The primary focus of environmental toxicological studies is to address the direct effects of chemicals on exposed organisms (parental generation - F0), mostly overlooking effects on subsequent non-exposed generations (F1 and F2 - intergenerational and F3 transgenerational, respectively). Here, we addressed the effects of simvastatin (SIM), one of the most widely prescribed human pharmaceuticals for the primary treatment of hypercholesterolemia, using the keystone crustacean Gammarus locusta. We demonstrate that SIM, at environmentally relevant concentrations, has significant inter and transgenerational (F1 and F3) effects in key signaling pathways involved in crustaceans' neuroendocrine regulation (Ecdysteroids, Catecholamines, NO/cGMP/PKG, GABAergic and Cholinergic signaling pathways), concomitantly with changes in apical endpoints, such as depressed reproduction and growth. These findings are an essential step to improve hazard and risk assessment of biological active compounds, such as SIM, and highlight the importance of studying the transgenerational effects of environmental chemicals in animals' neuroendocrine regulation.

A Real-Time, Plate-Based BRET Assay for Detection of cGMP in Primary Cells

Cyclic guanosine monophosphate (cGMP) is a second messenger involved in the regulation of numerous physiological processes. The modulation of cGMP is important in many diseases, but reliably assaying cGMP in live cells in a plate-based format with temporal resolution is challenging. The Förster/fluorescence resonance energy transfer (FRET)-based biosensor cGES-DE5 has a high temporal resolution and high selectivity for cGMP over cAMP, so we converted it to use bioluminescence resonance energy transfer (BRET), which is more compatible with plate-based assays. This BRET variant, called CYGYEL (cyclic GMP sensor using YFP-PDE5-Rluc8), was cloned into a lentiviral vector for use across different mammalian cell types. CYGYEL was characterised in HEK293T cells using the nitric oxide donor diethylamine NONOate (DEA), where it was shown to be dynamic, reversible, and able to detect cGMP with or without the use of phosphodiesterase inhibitors. In human primary vascular endothelial and smooth muscle cells, CYGYEL successfully detected cGMP mediated through either soluble or particulate guanylate cyclase using DEA or C-type natriuretic peptide, respectively. Notably, CYGYEL detected differences in kinetics and strength of signal both between ligands and between cell types. CYGYEL remained selective for cGMP over cAMP, but this selectivity was reduced compared to cGES-DE5. CYGYEL streamlines the process of cGMP detection in plate-based assays and can be used to detect cGMP activity across a range of cell types.

Angiotensin Receptor Blocker and Neprilysin Inhibitor Suppresses Cardiac Dysfunction by Accelerating Myocardial Angiogenesis in Apolipoprotein E-Knockout Mice Fed a High-Fat Diet

Materials and Methods

Male apolipoprotein E-knockout mice fed a high-fat diet were divided into control (CTL), valsartan (30 mg/kg) (VAL), sacubitril (30 mg/kg) (SAC), and valsartan plus sacubitril (30 mg/kg each) (VAL/SAC) groups after 4 weeks of prefeeding and were subsequently treated for 12 weeks.

Results

The VAL/SAC group exhibited significantly higher serum brain natriuretic peptide levels; more subtle changes in left ventricular systolic diameter, fractional shortening, and ejection fraction, and significantly higher expression levels of natriuretic peptide precursor B and markers of angiogenesis, including clusters of differentiation 34, vascular endothelial growth factor A, and monocyte chemotactic protein 1, than the CTL group.

Conclusions

Valsartan plus sacubitril preserved left ventricular systolic function in apolipoprotein E-knockout mice fed a high-fat diet. This result suggests that myocardial angiogenic factors induced by ARNI might provide cardioprotective effects.

Novel Antihypertension Mechanism of β-Glucan by Corin and ANP-Mediated Natriuresis in Mice

Many of the β-glucans are known to have antihypertensive activities, but, except for angiotensin-converting enzyme II inhibition, the underlying mechanisms remain unclear. Corin is an atrial natriuretic peptide (ANP)-converting enzyme. Activated corin cleaves pro-ANP to ANP, which regulates water-sodium balance and lowers blood pressure. Here, we reported a novel antihypertensive mechanism of β-glucans, involved with corin and ANP in mice. We showed that multiple oral administrations of β-glucan induced the expression of corin and ANP, and also increased natriuresis in mice. Microarray analysis showed that corin gene expression was only upregulated in mice liver by multiple, not single, oral administrations of the β-glucan fraction of Phellinus baumii (BGF). Corin was induced in liver and kidney tissues by the β-glucans from zymosan and barley, as well as by BGF. In addition to P. baumii, β-glucans from two other mushrooms, Phellinus linteus and Ganoderma lucidum, also induced corin mRNA expression in mouse liver. ELISA immunoassays showed that ANP production was increased in liver tissue by all the β-glucans tested, but not in the heart and kidney. Urinary sodium excretion was significantly increased by treatment with β-glucans in the order of BGF, zymosan, and barley, both in 1% normal and 10% high-sodium diets. In conclusion, we found that the oral administration of β-glucans could induce corin expression, ANP production, and sodium excretion in mice. Our findings will be helpful for investigations of β-glucans in corin and ANP-related fields, including blood pressure, salt-water balance, and circulation.

Effects of sacubitril/valsartan on ventricular remodeling in patents with left ventricular systolic dysfunction following acute anterior wall myocardial infarction

OBJECTIVE

The aim of this study was to investigate the effect of sacubitril/valsartan (Sal/Val) on left ventricular (LV) remodeling in patients with LV systolic dysfunction following acute anterior wall myocardial infarction (AAMI).

METHODS

AAMI patients with LV systolic dysfunction were enrolled in this study. All patients underwent percutaneous coronary intervention. After hemodynamic stabilization, patients were randomly assigned either to group T (Sal/Val treatment) or group C (enalapril treatment). Changes in echocardiographic parameters and plasma biochemical markers were used to evaluate the effects of Sal/Val on LV remodeling and cardiac function. The incidence of major cardiac adverse events (MACEs) and adverse reactions during follow-ups was also recorded.

RESULTS

In total, 137 eligible patients were prospectively included. Compared to group C, LV ejection fraction significantly improved (P < 0.05), while the LV end-systolic volume index and wall motion score index showed a tendency to decrease in group T. There was no difference in the LV end-diastolic volume index between groups. During follow-ups, the plasma N-terminal pro-B-type natriuretic peptide and soluble suppression of tumorigenesis-2 levels in both groups decreased (all P < 0.05), and the change was more prominent in group T. Additionally, drug-related adverse effects were similar between the two groups (P > 0.05); however, the incidence of MACEs was lower in group T than in group C (39.71% vs. 53.62%, P = 0.103), although the difference was insignificant.

CONCLUSION

Sac/Val attenuated LV remodeling and dysfunction and was safe and effective in LV systolic dysfunction patients post AAMI.

Type 5 phosphodiesterase (PDE5) and the vascular tree: From embryogenesis to aging and disease

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Vascular development depends on the timely differentiation of endothelial and smooth muscle cells.

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Vascular aging and vascular disease are influenced by endothelial and vascular smooth muscle cell compartments.

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A survey of the literature on the role of PDE5 in vascular development, aging and disease is reported.

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The role of PDE5 on vascular development, aging and disease needs to be further investigated by its genetic ablation.

Vascular tree development depends on the timely differentiation of endothelial and vascular smooth muscle cells. These latter are key players in the formation of the vascular scaffold that offers resistance to the blood flow. This review aims at providing an overview on the role of PDE5, the cGMP-specific phosphodiesterase that historically attracted much attention for its involvement in male impotence, in the regulation of vascular smooth muscle cell function. The overall goal is to underscore the importance of PDE5 expression and activity in this cell type in the context of the organs where its function has been extensively studied.

Estrogen and Bisphenol A in Hypertension

PURPOSE OF REVIEW

Cardiovascular disease (CVD) is a non-subsiding disease that remains a leading cause of morbidity and mortality. CVD has been associated with endocrine disruptors, such as bisphenol A (BPA). This review critically summarizes existing findings on BPA and hypertension, with particular attention to genomic, non-genomic, molecular, and cellular mechanisms of action that render BPA as a cardiovascular estrogenic disruptor.

RECENT FINDINGS

Owing to its similar estrogenic structure, BPA has been shown to affect various phenotypes that are regulated by the natural hormone, estrogen. Indeed, BPA has been shown to interact with estrogen receptors, located both in the cell membrane and in the cytoplasm/nucleus. Given that estrogen plays an important role in cardiovascular physiology, a contributing role for BPA in CVD would not be unexpected. Existing literature, though limited, established BPA as a source of disruption in cardiovascular health, particularly hypertension. However, effects of BPA are largely dependent on the dose, patient gender, tissue, and developmental stage of the exposed tissue/organ. Accumulating evidence argues for an adverse effect of BPA on blood pressure, with this effect being gender, dose, and time specific. Thus, comprehensive studies which take these factors and other parameters, like epigenetic factors, into account are warranted before a thorough understanding is at hand.

Maternal Overweight Downregulates MME (Neprilysin) in Feto-Placental Endothelial Cells and in Cord Blood

Maternal overweight in pregnancy alters the metabolic environment and generates chronic low-grade inflammation. This affects fetal development and programs the offspring’s health for developing cardiovascular and metabolic disease later in life. MME (membrane-metalloendopeptidase, neprilysin) cleaves various peptides regulating vascular tone. Endothelial cells express membrane-bound and soluble MME. In adults, the metabolic environment of overweight and obesity upregulates endothelial and circulating MME. We here hypothesized that maternal overweight increases MME in the feto-placental endothelium. We used primary feto-placental endothelial cells (fpEC) isolated from placentas after normal vs. overweight pregnancies and determined MME mRNA, protein, and release. Additionally, soluble cord blood MME was analyzed. The effect of oxygen and tumor necrosis factor α (TNFα) on MME protein in fpEC was investigated in vitro. Maternal overweight reduced MME mRNA (−39.9%, p < 0.05), protein (−42.5%, p = 0.02), and MME release from fpEC (−64.7%, p = 0.02). Both cellular and released MME protein negatively correlated with maternal pre-pregnancy BMI. Similarly, cord blood MME was negatively associated with pre-pregnancy BMI (r = −0.42, p = 0.02). However, hypoxia and TNFα, potential negative regulators of MME expression, did not affect MME protein. Reduction of MME protein in fpEC and in cord blood may alter the balance of vasoactive peptides. Our study highlights the fetal susceptibility to maternal metabolism and inflammatory state.

17β-Estradiol nongenomically induces vascular endothelial H2S release by promoting phosphorylation of cystathionine γ-lyase

Estrogen exerts its cardiovascular protective role at least in part by regulating endothelial hydrogen sulfide (H₂S) release, but the underlying mechanisms remain to be fully elucidated. Estrogen exerts genomic effects, i.e. those involving direct binding of the estrogen receptor (ER) to gene promoters in the nucleus, and nongenomic effects, mediated by interactions of the ER with other proteins. Here, using human umbilical vein endothelial cells (HUVECs), immunological detection, MS-based analyses, and cGMP and H₂S assays, we show that 17β-estradiol (E2) rapidly enhances endothelial H₂S release in a nongenomic manner. We found that E2 induces phosphorylation of cystathionine γ-lyase (CSE), the key enzyme in vascular endothelial H₂S generation. Mechanistically, E2 enhanced the interaction of membrane ERα with the Gα subunit Gαi-2/3, which then transactivated particulate guanylate cyclase-A (pGC-A) to produce cGMP, thereby activating protein kinase G type I (PKG-I). We also found that PKG-Iβ, but not PKG-Iα, interacts with CSE, leading to its phosphorylation, and rapidly induces endothelial H₂S release. Furthermore, we report that silencing of either CSE or pGC-A in mice attenuates E2-induced aorta vasodilation. These results provide detailed mechanistic insights into estrogen's nongenomic effects on vascular endothelial H₂S release and advance our current understanding of the protective activities of estrogen in the cardiovascular system.

The matrix environmental and cell mechanical properties regulate cell migration and contribute to the invasive phenotype of cancer cells

The minimal structural unit of a solid tumor is a single cell or a cellular compartment such as the nucleus. A closer look inside the cells reveals that there are functional compartments or even structural domains determining the overall properties of a cell such as the mechanical phenotype. The mechanical interaction of these living cells leads to the complex organization such as compartments, tissues and organs of organisms including mammals. In contrast to passive non-living materials, living cells actively respond to the mechanical perturbations occurring in their microenvironment during diseases such as fibrosis and cancer. The transformation of single cancer cells in highly aggressive and hence malignant cancer cells during malignant cancer progression encompasses the basement membrane crossing, the invasion of connective tissue, the stroma microenvironments and transbarrier migration, which all require the immediate interaction of the aggressive and invasive cancer cells with the surrounding extracellular matrix environment including normal embedded neighboring cells. All these steps of the metastatic pathway seem to involve mechanical interactions between cancer cells and their microenvironment. The pathology of cancer due to a broad heterogeneity of cancer types is still not fully understood. Hence it is necessary to reveal the signaling pathways such as mechanotransduction pathways that seem to be commonly involved in the development and establishment of the metastatic and mechanical phenotype in several carcinoma cells. We still do not know whether there exist distinct metastatic genes regulating the progression of tumors. These metastatic genes may then be activated either during the progression of cancer by themselves on their migration path or in earlier stages of oncogenesis through activated oncogenes or inactivated tumor suppressor genes, both of which promote the metastatic phenotype. In more detail, the adhesion of cancer cells to their surrounding stroma induces the generation of intracellular contraction forces that deform their microenvironments by alignment of fibers. The amplitude of these forces can adapt to the mechanical properties of the microenvironment. Moreover, the adhesion strength of cancer cells seems to determine whether a cancer cell is able to migrate through connective tissue or across barriers such as the basement membrane or endothelial cell linings of blood or lymph vessels in order to metastasize. In turn, exposure of adherent cancer cells to physical forces, such as shear flow in vessels or compression forces around tumors, reinforces cell adhesion, regulates cell contractility and restructures the ordering of the local stroma matrix that leads subsequently to secretion of crosslinking proteins or matrix degrading enzymes. Hence invasive cancer cells alter the mechanical properties of their microenvironment. From a mechanobiological point-of-view, the recognized physical signals are transduced into biochemical signaling events that guide cellular responses such as cancer progression after the malignant transition of cancer cells from an epithelial and non-motile phenotype to a mesenchymal and motile (invasive) phenotype providing cellular motility. This transition can also be described as the physical attempt to relate this cancer cell transitional behavior to a T1 phase transition such as the jamming to unjamming transition. During the invasion of cancer cells, cell adaptation occurs to mechanical alterations of the local stroma, such as enhanced stroma upon fibrosis, and therefore we need to uncover underlying mechano-coupling and mechano-regulating functional processes that reinforce the invasion of cancer cells. Moreover, these mechanisms may also be responsible for the awakening of dormant residual cancer cells within the microenvironment. Physicists were initially tempted to consider the steps of the cancer metastasis cascade as single events caused by a single mechanical alteration of the overall properties of the cancer cell. However, this general and simple view has been challenged by the finding that several mechanical properties of cancer cells and their microenvironment influence each other and continuously contribute to tumor growth and cancer progression. In addition, basement membrane crossing, cell invasion and transbarrier migration during cancer progression is explained in physical terms by applying physical principles on living cells regardless of their complexity and individual differences of cancer types. As a novel approach, the impact of the individual microenvironment surrounding cancer cells is also included. Moreover, new theories and models are still needed to understand why certain cancers are malignant and aggressive, while others stay still benign. However, due to the broad variety of cancer types, there may be various pathways solely suitable for specific cancer types and distinct steps in the process of cancer progression. In this review, physical concepts and hypotheses of cancer initiation and progression including cancer cell basement membrane crossing, invasion and transbarrier migration are presented and discussed from a biophysical point-of-view. In addition, the crosstalk between cancer cells and a chronically altered microenvironment, such as fibrosis, is discussed including the basic physical concepts of fibrosis and the cellular responses to mechanical stress caused by the mechanically altered microenvironment. Here, is highlighted how biophysical approaches, both experimentally and theoretically, have an impact on classical hallmarks of cancer and fibrosis and how they contribute to the understanding of the regulation of cancer and its progression by sensing and responding to the physical environmental properties through mechanotransduction processes. Finally, this review discusses various physical models of cell migration such as blebbing, nuclear piston, protrusive force and unjamming transition migration modes and how they contribute to cancer progression. Moreover, these cellular migration modes are influenced by microenvironmental perturbances such as fibrosis that can induce mechanical alterations in cancer cells, which in turn may impact the environment. Hence, the classical hallmarks of cancer need to be refined by including biomechanical properties of cells, cell clusters and tissues and their microenvironment to understand mechano-regulatory processes within cancer cells and the entire organism.

Angiotensin Receptor Neprilysin Inhibitor Attenuates Myocardial Remodeling and Improves Infarct Perfusion in Experimental Heart Failure

Angiotensin receptor blocker-neprilysin inhibitor (ARNi) therapy improves the prognosis of heart failure patients. However, the mechanisms remain unclear. This study investigated the biological effects of ARNi with neprilysin inhibitor sacubitril and angiotensin receptor blocker valsartan on myocardial remodeling and cardiac perfusion in experimental heart failure (HF) after myocardial infarction (MI). Male Lewis rats (10-weeks old) with confirmed HF were randomized one-week post-MI to treatment with vehicle (water), sacubitril/valsartan or valsartan, as comparator group, for either 1 or 5 weeks. Sacubitril/valsartan for 1-week limited LV contractile dysfunction vs. vehicle and both sacubitril/valsartan and valsartan attenuated progressive LV dilation after 1 and 5 weeks treatment. After 5 weeks, both sacubitril/valsartan and valsartan reduced CTGF expression in the remote myocardium, although only sacubitril/valsartan prevented interstitial fibrosis. In the border zone, sacubitril/valsartan and valsartan reduced hypertrophic markers, but only sacubitril/valsartan reduced cardiomyocyte size and increased VEGFA expression. In the infarct, sacubitril/valsartan induced an early uptake of 99mTc-NC100692 (a radiotracer of angiogenesis) and improved perfusion, as determined by 201Tl microSPECT/CT imaging. In conclusion, ARNi improved global LV function, limited remodeling in the remote and border zones, and increased perfusion to the infarct. Sacubitril/valsartan had more consistent effects than valsartan on LV remodeling in experimental HF.

Filopodia and focal adhesions: An integrated system driving branching morphogenesis in neuronal pathfinding and angiogenesis

Single cell branching during development in vertebrates is typified by neuronal branching to form neurites and vascular branches formed by sprouting angiogenesis. Neurons and endothelial tip cells possess subcellular protrusions that share many common features from the morphological to the molecular level. Both systems utilize filopodia as their cellular protrusion organelles and depend on specific integrin-mediated adhesions to the local extracellular matrix for guidance in their pathfinding. We discuss the similar molecular machineries involved in these two types of cell branch formation and use their analogy to propose a new mechanism for angiogenic filopodia function, namely as adhesion assembly sites. In support of this model we provide primary data of angiogenesis in zebrafish in vivo showing that the actin assembly factor VASP participates in both filopodia formation and adhesion assembly at the base of the filopodia, enabling forward progress of the tip cell. The use of filopodia and their associated adhesions provide a common mechanism for neuronal and endothelial pathfinding during development in response to extracellular matrix cues.

Genome-Wide Prioritization and Transcriptomics Reveal Novel Signatures Associated With Thiazide Diuretics Blood Pressure Response

BACKGROUND

Thiazide diuretics are among the most commonly prescribed antihypertensives. However, <50% of thiazide-treated patients achieve blood pressure (BP) control. Herein, we used different omics (genomics and transcriptomics) to identify novel biomarkers of thiazide diuretics BP response.

METHODS AND RESULTS

Genome-wide analysis included 228 white hypertensives with BP determined at baseline and after 9 weeks of hydrochlorothiazide. Single-nucleotide polymorphisms with P <5×10^-5 were prioritized according to their biological function, using RegulomeDB, haploreg, and Genome-Wide Annotation of Variants. The results from the prioritization approach revealed rs10995 as the most likely functional single-nucleotide polymorphism, among single-nucleotide polymorphisms tested, that has been associated with hydrochlorothiazide BP response. The rs10995 G-allele was associated with better BP response to hydrochlorothiazide versus noncarriers (Δ systolic BP/Δ diastolic BP: -12.3/-8.2 versus -6.8/-3.5 mm Hg, respectively, Δ systolic BP P=3×10^-4, Δ diastolic BP P=5×10^-5). This association was replicated in independent participants treated with chlorthalidone. In addition, rs10995 G-allele was associated with increased mRNA expression of VASP (vasodilator-stimulated phosphoprotein). Moreover, baseline expression of the VASP mRNA was significantly higher in 25 good responders to hydrochlorothiazide compared with 25 poor responders (P=0.01). This finding was replicated in independent participants treated with chlorthalidone (P=0.04). Last, allelic-specific expression analysis revealed a significant but modest imbalance with rs10995 and rs10156, a single-nucleotide polymorphism in high linkage disequilibrium (r²=0.7) with rs10995, which both could contribute to the observed genetic effects by affecting VASP mRNA expression.

CONCLUSIONS

This study highlights the strength of using different omics to identify novel biomarkers of drug response and suggests VASP as a potential determinant of thiazide diuretics BP response.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifiers: NCT00246519 and NCT01203852.

C-Type Natriuretic Peptide Induces Anti-contractile Effect Dependent on Nitric Oxide, Oxidative Stress, and NPR-B Activation in Sepsis

AIMS

To evaluate the role of nitric oxide, reactive oxygen species (ROS), and natriuretic peptide receptor-B activation in C-type natriuretic peptide-anti-contractile effect on Phenylephrine-induced contraction in aorta isolated from septic rats.

METHODS AND RESULTS

Cecal ligation and puncture (CLP) surgery was used to induce sepsis in male rats. Vascular reactivity was conducted in rat aorta and resistance mesenteric artery (RMA). Measurement of survival rate, mean arterial pressure (MAP), plasma nitric oxide, specific protein expression, and localization were evaluated. Septic rats had a survival rate about 37% at 4 h after the surgery, and these rats presented hypotension compared to control-operated (Sham) rats. Phenylephrine-induced contraction was decreased in sepsis. C-type natriuretic peptide (CNP) induced anti-contractile effect in aortas. Plasma nitric oxide was increased in sepsis. Nitric oxide-synthase but not natriuretic peptide receptor-B expression was increased in septic rat aortas. C-type natriuretic peptide-anti-contractile effect was dependent on nitric oxide-synthase, ROS, and natriuretic peptide receptor-B activation. Natriuretic peptide receptor-C, protein kinase-Cα mRNA, and basal nicotinamide adenine dinucleotide phosphate (NADPH)-dependent ROS production were lower in septic rats. Phenylephrine and CNP enhanced ROS production. However, stimulated ROS production was low in sepsis.

CONCLUSION

CNP induced anti-contractile effect on Phenylephrine contraction in aortas from Sham and septic rats that was dependent on nitric oxide-synthase, ROS, and natriuretic peptide receptor-B activation.

Matrix Metalloproteinase 9 and Vasodilator-Stimulated Phosphoprotein Related to Acute Kidney Injury in Severe Acute Pancreatitis Rats

BACKGROUND

Severe acute pancreatitis (SAP) usually results in acute renal failure. Matrix metalloproteinase 9 (MMP-9) and vasodilator-stimulated phosphoprotein (VASP) may participate in disease progression.

AIM

To investigate the renal expression of MMP-9 and VASP in SAP rats with acute kidney injury.

METHODS

A total of 100 rats were randomly assigned to sham 6-h, sham 12-h, sham 24-h, sham 36-h, sham 48-h, SAP 6-h, SAP 12-h, SAP 24-h, SAP 36-h, and SAP 48-h treatment groups (n = 10 per group). Levels of serum amylase (AMY), creatinine (Cr), and blood urea nitrogen (BUN) were determined. Renal pathology and ultrastructural examinations were performed, and renal mRNA and protein expression of MMP-9 and VASP were determined by real-time RT-PCR and Western blot, respectively. The activity of MMP-9 was assessed by gelatin zymography.

RESULTS

In the SAP groups, serum levels of AMY, Cr, and BUN were markedly higher than in the sham groups. The peak value of AMY was observed from 12 to 24 h, but that of Cr and BUN was observed at 36 h. Capillary endothelial cells in the renal interstitium were impaired and expression of MMP-9 and VASP in the kidney was significantly increased when compared with the sham groups. Expression of MMP-9 and VASP declined when renal damage reached a maximum after 24 h.

CONCLUSIONS

In the presence of acute kidney injury in SAP, the renal expression of MMP-9 and VASP is related to damage of endothelial cells in capillaries, which reached a maximum at 24 h and declined afterwards.

Scutellarin's Cardiovascular Endothelium Protective Mechanism: Important Role of PKG-Iα

Scutellarin (SCU), a flavonoid glycoside compound, has been successfully used in clinic for treatment of ischemic diseases in China. In this report, we checked the effects of SCU on endothelium dysfunction (ED) of coronary artery (CA) against myocardial ischemia reperfusion (MIR) injury in vivo. The involvement of PKG-Iα was further studied using cultured endothelial cells subjected to hypoxia reoxygenation (HR) injury in vitro. In rat MIR model, SCU (45 and 90 mg/kg, iv) significantly reduced ischemic size and restored the endothelium-dependent vasodilation of isolated CA rings. PKG inhibitor Rp-8-Br-cGMP (50 μg/kg, iv) could ameliorate the protective effects of SCU. Increase in phosphorylation of vasodilator-stimulated phosphoprotein (VASP), a main substrate of PKG, at Ser 239 was observed in both heart tissue and serum of SCU-treated animals. In cultured human cardiac microvascular endothelial cells (HCMECs), SCU (1 and 10 μM) dose-dependently protected cell viability and increased the mRNA and protein level of PKG-Iα against HR injury. The activity of PKG was also increased by SCU treatment. The activation of PKG–1α was then studied using targeted proteomic analysis (MRM-MS) checking the phosphorylation state of the autophosphorylation domain (aa42-94). Significant decrease in phosphorylation of PKG-Iα at Ser50, Ser72, Ser89 was induced by HR injury while SCU treatment significantly increased the phosphorylation of PKG-Iα, not only at Ser50, Ser72 and Ser89, but also at Ser44 and Thr58 (two novel phosphorylation domains). Our results demonstrate PKG-Iα might play an important role in the protective effects of SCU on ED against MIR injury.

Factors Associated with Nitric Oxide-mediated β2 Integrin Inhibition of Neutrophils

This investigation explored the mechanism for inhibition of β2 integrin adhesion molecules when neutrophils are exposed to nitric oxide ((•)NO). Roles for specific proteins were elucidated using chemical inhibitors, depletion with small inhibitory RNA, and cells from knock-out mice. Optimal inhibition occurs with exposures to a (•)NO flux of ∼ 28 nmol/min for 2 min or more, which sets up an autocatalytic cascade triggered by activating type 2 nitric-oxide synthase (NOS-2) and NADPH oxidase (NOX). Integrin inhibition does not occur with neutrophils exposed to a NOX inhibitor (Nox2ds), a NOS-2 inhibitor (1400 W), or with cells from mice lacking NOS-2 or the gp91(phox) component of NOX. Reactive species cause S-nitrosylation of cytosolic actin that enhances actin polymerization. Protein cross-linking and actin filament formation assays indicate that increased polymerization occurs because of associations involving vasodilator-stimulated phosphoprotein, focal adhesion kinase, and protein-disulfide isomerase in proximity to actin filaments. These effects were inhibited in cells exposed to ultraviolet light which photo-reverses S-nitrosylated cysteine residues and by co-incubations with cytochalasin D. The autocatalytic cycle can be arrested by protein kinase G activated with 8-bromo-cyclic GMP and by a high (•)NO flux (∼ 112 nmol/min) that inactivates NOX.

Atrial natriuretic peptide and aldosterone synthase gene in essential hypertension: a case-control study

The renin-angiotensin-aldosterone system (RAAS) and their candidate genes are principally involved in regulation of blood pressure through salt-water homeostasis. Atrial natriuretic peptide (ANP) and Aldosterone synthase (CYP11B2) are the important RAAS mediators, play a major role in hypertension through regulation of cardiorenal homeostasis and water-electrolytes balance, respectively. Present study reports the expression of ANP and CYP11B2 gene at mRNA and proteins levels in patients with essential hypertension in North Indian subjects. Gene expression at mRNA and protein levels was carried out by Real time PCR and Western blot, respectively. We found a significant down regulation in the ANP gene expression at mRNA (85%) and protein (72.6%) levels and significant increase in the CYP11B2 protein expression in patients as compared to controls. A significant increase in Serum creatinine (14.6%), Sodium (1.15%) and decrease in the Blood urea (8.18%) and Potassium (2.32%) levels were also observed among the patients group having higher expression (based on median delta-CT value) in comparison to the lower expression of CYP11B2 gene. Our results suggest that the down-regulation of ANP gene expression at mRNA and protein levels and up-regulated CYP11B2 protein expression levels may be correlated with the essential hypertension and could serve as circulating prognostic biomarkers for essential hypertension.

Dipyridamole-induced C-type natriuretic peptide mRNA overexpression in a minipig model of pacing-induced left ventricular dysfunction

Dipyridamole (DP) restores ischemic tissue blood flow stimulating angiogenesis in eNOS-dependent pathways. C-type natriuretic peptide (CNP) is expected to mimic the migration-stimulatory effect of NO via a cGMP-dependent mechanism. Aim of this study was to assess the role of concomitant treatment with DP on CNP levels in blood and myocardial tissue of minipigs with left ventricular dysfunction (LVD) induced by pacing at 200bpm in the right ventricular apex. Minipigs with DP therapy (DP+, n=4) or placebo (DP-, n=4) and controls (C-SHAM, n=4) underwent 2D-EchoDoppler examination and blood collection before and after 4 weeks of pacing, when cardiac tissue was collected. Histological/immunohistochemical analyses were performed. CNP levels were determined by radioimmunoassay; cardiac CNP, BNP, natriuretic receptors expression by Real-Time PCR. After pacing, cardiac parameters resulted less impaired in DP+ compared to DP-. Histological sections presented normal morphology while the arteriolar density resulted: C-SHAM: 9.0±1.2; DP-: 4.9±0.3; DP+: 6.5±0.6number/mm(2); C-SHAM vs DP- and DP+ p=0.004, p=0.04, respectively. CNP mRNA resulted lower in DP- compared to C-SHAM and DP+ as well as NPR-B (p=0.011, DP- vs DP+). Both NPR-A/NPR-C mRNA expressions were significantly (p<0.001) lower both in DP- and DP+ compared to C-SHAM. BNP mRNA was higher in LVD. CNP plasma levels showed a similar trend with respect to gene expression (C-SHAM: 30.5±15; DP-: 18.6±5.5; DP+: 21.2±4.7pg/ml). These data suggest that DP may serve as a preconditioning agent to increase the protective CNP-mediated endocrine response in LVD. This response, mediated by its specific receptor NPR-B, may offer new insights into molecular targets for treatment of LVD.

PDE2 is a novel target for attenuating tumor formation in a mouse model of UVB-induced skin carcinogenesis

Our previous studies demonstrated that the topical application of caffeine is a potent inhibitor of UVB-induced carcinogenesis and selectively increases apoptosis in tumors but not in non-tumor areas of the epidermis in mice that are at a high risk for developing skin cancer. While this effect is mainly through a p53 independent pathway, the mechanism by which caffeine inhibits skin tumor formation has not been fully elucidated. Since caffeine is a non-specific phosphodiesterase inhibitor, we investigated the effects of several PDE inhibitors on the formation of sunburn cells in mouse skin after an acute exposure to ultraviolet light B (UVB). The topical application of a PDE2 inhibitor, erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride (EHNA hydrochloride), stimulated epidermal apoptosis compared to control (P<0.01) and to a greater extent than caffeine whereas a PDE4 inhibitor attenuated the epidermal apoptosis compared to control (P<0.01). Since PDE2 hydrolyzes cyclic nucleotides, mainly cGMP, the effects of EHNA hydrochloride on epidermal apoptosis following UVB exposure may be mediated, in part, by increased cGMP signaling. Data demonstrated that the topical application of dibutyryl cGMP stimulated epidermal apoptosis (P<0.01) following an acute exposure to UVB. Treating UVB-pretreated mice topically with 3.1 µmole or 0.8 µmole of EHNA hydrochloride attenuated tumor formation to a greater extent than treating with 6.2 µmole caffeine when these compounds were applied once a day, five days a week for 18 weeks. These observations suggest a novel role for PDE2 in UVB-induced tumorigenesis and that PDE2 inhibitors that mediate cGMP signaling may be useful for the prevention and treatment of skin cancer.

Natriuretic peptide receptor A signaling regulates stem cell recruitment and angiogenesis: a model to study linkage between inflammation and tumorigenesis

Natriuretic peptide receptor A (NPRA), the signaling receptor for the cardiac hormone, atrial natriuretic peptide (ANP), is expressed abundantly in inflamed/injured tissues and tumors. NPRA deficiency substantially decreases tissue inflammation and inhibits tumor growth. However, the precise mechanism of NPRA function and whether it links inflammation and tumorigenesis remains unknown. Since both injury repair and tumor growth require stem cell recruitment and angiogenesis, we examined the role of NPRA signaling in tumor angiogenesis as a model of tissue injury repair in this study. In in vitro cultures, aortas from NPRA-KO mice show significantly lower angiogenic response compared to wild-type counterparts. The NPRA antagonist that decreases NPRA expression, inhibits lipopolysaccharide-induced angiogenesis. The reduction in angiogenesis correlates with decreased expression of vascular endothelial growth factor and chemokine (C-X-C motif) receptor 4 (CXCR4) implicating a cell recruitment defect. To test whether NPRA regulates migration of cells to tumors, mesenchymal stem cells (MSCs) were administered i.v., and the results showed that MSCs fail to migrate to the tumor microenvironment in NPRA-KO mice. However, coimplanting tumor cells with MSCs increases angiogenesis and tumorigenesis in NPRA-KO mice, in part by promoting expression of CXCR4 and its ligand, stromal cell-derived factor 1α. Taken together, these results demonstrate that NPRA signaling regulates stem cell recruitment and angiogenesis leading to tumor growth. Thus, NPRA signaling provides a key linkage between inflammation and tumorigenesis, and NPRA may be a target for drug development against cancers and tissue injury repair.

Nitric oxide/cyclic GMP signaling regulates motility of a microglial cell line and primary microglia in vitro

Microglia are the resident immune cells of the brain, which become rapidly activated and migrate to the site of insult in brain infection and disease. Activated microglia generate large amounts of the highly reactive messenger molecule nitric oxide (NO). NO is able to raise cyclic GMP levels via binding to soluble guanylyl cyclase. We investigated potential mechanistic links between inflammation, NO signaling, and microglial migration. To monitor cell migration, we used a scratch wound assay and compared results obtained in the BV-2 microglial line to primary microglia. Incubation with lipopolysaccharide (LPS) as stimulator of acute inflammatory processes enhanced migration of both microglial cell types. LPS activated NO production in BV-2 cells and application of an NO donor increased BV-2 cell migration while an NO scavenger reduced motility. Pharmacological inhibition of soluble guanylyl cyclase and the resulting decrease in motility can be rescued by a membrane permeant analog of cGMP. Despite differences in the threshold towards stimulation with the chemical agents, both BV-2 cells and primary microglia react in a similar way. The important role of NO/cGMP as positive regulator of microglial migration, the downstream targets of the signaling cascade, and resulting cytoskeletal changes can be conveniently investigated in a microglial cell line.

Levels of brain natriuretic peptide are associated with peripheral arterial disease in subjects with type-2 diabetes mellitus

BACKGROUND

The effects of brain natriuretic peptide (BNP) on the risk of cardiovascular disease and atherosclerosis have been studied. However, little information is available regarding peripheral arterial disease (PAD), particularly among subjects with type-2 diabetes mellitus (T2DM). The aim of our study was to assess the potential relationship between BNP levels and PAD among T2DM patients.

METHODS

The study cohort was 507 T2DM outpatients in which BNP levels were measured. Cross-sectional associations between BNP levels (in tertiles) and PAD were examined.

RESULTS

Compared withT2DM patients without PAD, BNP levels were markedly higher in patients with PAD (p = 0.001). Correlation analyses showed that the BNP level was negatively correlated with the ankle-brachial index (r = -0.453, p = 0.033). At a cutoff value of 78.2 pg/ml, the BNP level showed a sensitivity of 71.9%, a specificity of 68.1%, and a positive predictive value of 84.3% for a diagnosis of PAD. The area under the receiver-operating characteristic curve increased significantly if BNP levels were incorporated into a predictive model of the potential risk factors for PAD (0.85 vs 0.81, p = 0.029).

CONCLUSIONS

BNP is a potential and promising biomarker for PAD screening in T2DM patients.

The role of cyclic nucleotide signaling pathways in cancer: targets for prevention and treatment

For more than four decades, the cyclic nucleotides cyclic AMP (cAMP) and cyclic GMP (cGMP) have been recognized as important signaling molecules within cells. Under normal physiological conditions, cyclic nucleotides regulate a myriad of biological processes such as cell growth and adhesion, energy homeostasis, neuronal signaling, and muscle relaxation. In addition, altered cyclic nucleotide signaling has been observed in a number of pathophysiological conditions, including cancer. While the distinct molecular alterations responsible for these effects vary depending on the specific cancer type, several studies have demonstrated that activation of cyclic nucleotide signaling through one of three mechanisms-induction of cyclic nucleotide synthesis, inhibition of cyclic nucleotide degradation, or activation of cyclic nucleotide receptors-is sufficient to inhibit proliferation and activate apoptosis in many types of cancer cells. These findings suggest that targeting cyclic nucleotide signaling can provide a strategy for the discovery of novel agents for the prevention and/or treatment of selected cancers.

A comparative study of NONOate based NO donors: spermine NONOate is the best suited NO donor for angiogenesis

Nitric oxide (NO) is a known modulator of angiogenesis. The NONOate subfamily of NO donors has long been used in experimental and clinical studies to promote angiogenesis. However, no studies have been conducted yet to compare the angiogenesis potential of these NO donors in respect to their pattern of NO release. We hypothesize that having different pattern of NO release, each of the NO donors in NONOate subfamily can promote key stages of angiogenesis in differential manner. To verify our hypothesis, NO donors with half life ranging from seconds to several hours and having very different pattern of NO release were selected to evaluate their efficacy in modulating angiogenesis. Endothelial tube formation using EAhy926 cells was maximally increased by Spermine NONOate (SP) treatment. SP treatment maximally induced both ex vivo and in vivo angiogenesis using egg yolk and cotton plug angiogenesis models respectively. Experiment using chick embryo partial ischemia model revealed SP as the best suited NO donor to recover ischemia driven hampered angiogenesis. The present study elaborated that differential release pattern of NO by different NO donors can modulate angiogenesis differentially and also suggested that SP have a unique pattern of NO release that best fits for angiogenesis.

Nitric oxide directly promotes vascular endothelial insulin transport

Insulin resistance strongly associates with decreased nitric oxide (NO) bioavailability and endothelial dysfunction. In the vasculature, NO mediates multiple processes that affect insulin delivery, including dilating both resistance and terminal arterioles in skeletal muscle in vivo. However, whether NO directly regulates vascular endothelial cell (EC) insulin uptake and its transendothelial transport (TET) is unknown. We report in this article that L-N(G)-nitro-L-arginine methyl ester (L-NAME) pretreatment blocked, whereas L-arginine and sodium nitroprusside (SNP) each enhanced, EC uptake of fluorescein isothiocyanate (FITC)-labeled insulin. SNP also partly or fully reversed the inhibition of EC insulin uptake caused by L-NAME, wortmannin, the Src inhibitor PP1, and tumor necrosis factor-α. In addition, SNP promoted [(125)I]Tyr(A14)insulin TET by ~40%. Treatment with insulin with and without SNP did not affect EC cyclic guanosine monophosphate (cGMP) levels, and the cGMP analog 8-bromo-cGMP did not affect FITC-insulin uptake. In contrast, treatment with insulin and SNP significantly increased EC protein S-nitrosylation, the colocalization of S-nitrosothiol (S-NO) and protein-tyrosine phosphatase 1B (PTP1B), and Akt phosphorylation at Ser(473) and inhibited PTP1B activity. Moreover, a high-fat diet significantly inhibited EC insulin-stimulated Akt phosphorylation and FITC-insulin uptake that was partially reversed by SNP in rats. Finally, inhibition of S-nitrosylation by knockdown of thioredoxin-interacting protein completely eliminated SNP-enhanced FITC-insulin uptake. We conclude that NO directly promotes EC insulin transport by enhancing protein S-nitrosylation. NO also inhibits PTP1B activity, thereby enhancing insulin signaling.

Modulation of thioacetamide-induced liver fibrosis/cirrhosis by sildenafil treatment

Sildenafil citrate is a phosphodiesterase-5 inhibitor, approved for the treatment of erectile dysfunction. It enhances nitric-oxide-induced vasodilatation and it promotes angiogenesis. A relationship between angiogenesis and hepatic fibrosis has long been speculated, where the 2 are believed to progress together. In this study, the ability of sildenafil (10 mg·(kg body mass)(-1), orally, once daily) to prevent and also reverse liver fibrosis/cirrhosis experimentally induced by thioacetamide injection (200 mg·kg(-1), intraperitoneal (i.p.), 3 times·week(-1)) in male Sprague-Dawley rats has been investigated. Sildenafil administration, either to prevent or to reverse liver fibrosis/cirrhosis significantly improved the estimated hepatic functions, reduced hepatic hydroxyproline and, in turn, hepatic collagen content, as well as reducing serum levels of the pro-fibrogenic mediator transforming growth factor β1. In co-ordination with such improvement, fibrosis grades declined and fibrosis retracted. Herein, the observed results provide evidence for the potential therapeutic efficacy of sildenafil as an antifibrotic agent.

AMP-activated protein kinase regulates L-arginine mediated cellular responses

Background

Our prior study revealed the loss in short-term L-Arginine (ARG) therapeutic efficacy after continuous exposure; resulting in tolerance development, mediated by endothelial nitric oxide synthase (eNOS) down-regulation, secondary to oxidative stress and induced glucose accumulation. However, the potential factor regulating ARG cellular response is presently unknown.

Method

Human umbilical vein endothelial cells were incubated with 100 μM ARG for 2 h in buffer (short-term or acute), or for 7 days in culture medium and challenged for 2 h in buffer (continuous or chronic), in the presence or absence of other agents. eNOS activity was determined by analyzing cellular nitrite/nitrate (NO₂^–/NO₃^–), and AMP-activated protein kinase (AMPK) activity was assayed using SAMS peptide. ¹³C₆ glucose was added to medium to measure glucose uptake during cellular treatments, which were determined by LC-MS/MS. Cellular glucose was identified by o-toluidine method. Superoxide (O₂^•–) was identified by EPR-spin-trap, and peroxynitrite (ONOO^–) was measured by flow-cytometer using aminophenyl fluorescein dye.

Results

Short-term incubation of cells with 100 μM ARG in the presence or absence of 30 μM L-N^G-Nitroarginine methyl ester (L-NAME) or 30 μM AMPK inhibitor (compound C, CMP-C) increased cellular oxidative stress and overall glucose accumulation with no variation in glucose transporter-1 (GLUT-1), or AMPK activity from control. The increase in total NO₂^–/NO₃^– after 2 h 100 μM ARG exposure, was suppressed in cells co-incubated with 30 μM CMP-C or L-NAME. Long-term exposure of ARG with or without CMP-C or L-NAME suppressed NO₂^–/NO₃^–, glucose uptake, GLUT-1, AMPK expression and activity below control, and increased overall cellular glucose, O₂^•– and ONOO^–. Gluconeogenesis inhibition with 30 μM 5-Chloro-2-N-2,5-dichlorobenzenesulfonamido-benzoxazole (CDB) during ARG exposure for 2 h maintained overall cellular glucose to control, but increased cellular glucose uptake. Continuous co-incubation with CDB and ARG increased NO₂^–/NO₃^–, glucose uptake, GLUT-1, AMPK expression and activity, and maintained overall cellular glucose, O₂^•– and ONOO^– to control conditions.

Conclusion

The present study provides the fundamental evidence for AMPK as the primary modulator of ARG cellular responses and for regulating the mode of glucose accumulation during short-term and continuous ARG treatments.

Nitric oxide regulates cardiac intracellular Na⁺ and Ca²⁺ by modulating Na/K ATPase via PKCε and phospholemman-dependent mechanism

In the heart, Na/K-ATPase regulates intracellular Na⁺ and Ca^2 + (via NCX), thereby preventing Na⁺ and Ca^2 + overload and arrhythmias. Here, we test the hypothesis that nitric oxide (NO) regulates cardiac intracellular Na⁺ and Ca^2 + and investigate mechanisms and physiological consequences involved. Effects of both exogenous NO (via NO-donors) and endogenously synthesized NO (via field-stimulation of ventricular myocytes) were assessed in this study. Field stimulation of rat ventricular myocytes significantly increased endogenous NO (18 ± 2 μM), PKCε activation (82 ± 12%), phospholemman phosphorylation (at Ser-63 and Ser-68) and Na/K-ATPase activity (measured by DAF-FM dye, western-blotting and biochemical assay, respectively; p < 0.05, n = 6) and all were abolished by Ca^2 +-chelation (EGTA 10 mM) or NOS inhibition l-NAME (1 mM). Exogenously added NO (spermine-NONO-ate) stimulated Na/K-ATPase (EC50 = 3.8 μM; n = 6/grp), via decrease in K_m, in PLM^WT but not PLM^KO or PLM^3SA myocytes (where phospholemman cannot be phosphorylated) as measured by whole-cell perforated-patch clamp. Field-stimulation with l-NAME or PKC-inhibitor (2 μM Bis) resulted in elevated intracellular Na⁺ (22 ± 1.5 and 24 ± 2 respectively, vs. 14 ± 0.6 mM in controls) in SBFI-AM-loaded rat myocytes. Arrhythmia incidence was significantly increased in rat hearts paced in the presence of l-NAME (and this was reversed by l-arginine), as well as in PLM^3SA mouse hearts but not PLM^WT and PLM^KO. We provide physiological and biochemical evidence for a novel regulatory pathway whereby NO activates Na/K-ATPase via phospholemman phosphorylation and thereby limits Na⁺ and Ca^2 + overload and arrhythmias. This article is part of a Special Issue entitled “Na⁺ Regulation in Cardiac Myocytes”.

•

We tested whether nitric oxide regulates intracellular Na⁺ and Ca^2 + in the heart.

•

Nitric oxide increased Na/K ATPase activity via PKCε-induced phospholemman phosphorylation.

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Inhibiting nitric oxide pathway resulted in Na⁺ and Ca^2 + overload and contributed to arrhythmia development in the heart.

Compartmentalization of cyclic nucleotide signaling: a question of when, where, and why?

Preciseness of cellular behavior depends upon how an extracellular cue mobilizes a correct orchestra of cellular messengers and effector proteins spatially and temporally. This concept, termed compartmentalization of cellular signaling, is now known to form the molecular basis of many aspects of cellular behavior in health and disease. The cyclic nucleotides cyclic adenosine monophosphate and cyclic guanosine monophosphate are ubiquitous cellular messengers that can be compartmentalized in three ways: first, by their physical containment; second, by formation of multiple protein signaling complexes; and third, by their selective depletion. Compartmentalized cyclic nucleotide signaling is a very prevalent response among all cell types. In order to understand how it becomes relevant to cellular behavior, it is important to know how it is executed in cells to regulate physiological responses and, also, how its execution or dysregulation can lead to a pathophysiological condition, which forms the scope of the presented review.

The sGC activator BAY 60-2770 has potent erectile activity in the rat

Nitric oxide (NO) is the principal mediator of penile erection, and soluble guanylate cyclase (sGC) is the receptor for NO. In pathophysiological conditions when sGC is inactivated and not responsive to NO or sGC stimulators a new class of agents called sGC activators increase the activity of NO-insensitive sGC and produce erection. The aim of this study was to investigate erectile responses to BAY 60-2770, a sGC activator, under physiological and pathophysiological conditions. In the present study increases in intracavernosal pressure (ICP) in response to intracavernosal (ic) injections of BAY 60-2770 were investigated under baseline conditions, when sGC was inhibited by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), when nitric oxide synthase (NOS) was inhibited by N-nitro-L-arginine methyl ester (L-NAME), and after cavernosal nerve crush injury. Under baseline conditions ic injections of BAY 60-2770 increase ICP, ICP/mean arterial pressure (MAP), and area under the ICP curve (AUC) and produce small decreases in MAP at the highest doses studied. BAY 60-2770 was very potent in its ability to induce erection and responses to BAY 60-2770 were enhanced by ODQ which attenuates erectile responses to sodium nitroprusside (SNP), diethylamine NONOate (DEA/NO), and cavernosal nerve stimulation. Responses to BAY 60-2770 were not altered by L-NAME or cavernosal nerve crush injury. These data indicate that BAY 60-2770 has potent erectile activity that is enhanced by ODQ and show that responses to BAY 60-2770 are not attenuated by NOS inhibition or cavernosal nerve injury. These results suggest that BAY 60-2770 would be effective in the treatment of erectile dysfunction when NO bioavailability is reduced, after pelvic nerve injury, and when sGC is oxidized.

Endothelial actions of atrial and B-type natriuretic peptides

The cardiac hormone atrial natriuretic peptide (ANP) is critically involved in the maintenance of arterial blood pressure and intravascular volume homeostasis. Its cGMP-producing GC-A receptor is densely expressed in the microvascular endothelium of the lung and systemic circulation, but the functional relevance is controversial. Some studies reported that ANP stimulates endothelial cell permeability, whereas others described that the peptide attenuates endothelial barrier dysfunction provoked by inflammatory agents such as thrombin or histamine. Many studies in vitro addressed the effects of ANP on endothelial proliferation and migration. Again, both pro- and anti-angiogenic properties were described. To unravel the role of the endothelial actions of ANP in vivo, we inactivated the murine GC-A gene selectively in endothelial cells by homologous loxP/Cre-mediated recombination. Our studies in these mice indicate that ANP, via endothelial GC-A, increases endothelial albumin permeability in the microcirculation of the skin and skeletal muscle. This effect is critically involved in the endocrine hypovolaemic, hypotensive actions of the cardiac hormone. On the other hand the homologous GC-A-activating B-type NP (BNP), which is produced by cardiac myocytes and many other cell types in response to stressors such as hypoxia, possibly exerts more paracrine than endocrine actions. For instance, within the ischaemic skeletal muscle BNP released from activated satellite cells can improve the regeneration of neighbouring endothelia. This review will focus on recent advancements in our understanding of endothelial NP/GC-A signalling in the pulmonary versus systemic circulation. It will discuss possible mechanisms accounting for the discrepant observations made for the endothelial actions of this hormone-receptor system and distinguish between (patho)physiological and pharmacological actions. Lastly it will emphasize the potential therapeutical implications derived from the actions of NPs on endothelial permeability and regeneration.

Phosphorylation of vasodilator-stimulated phosphoprotein (VASP) dampens hepatic ischemia-reperfusion injury

Recent work has demonstrated that the formation of platelet neutrophil complexes (PNCs) affects inflammatory tissue injury. Vasodilator-stimulated phosphoprotein (VASP) is crucially involved into the control of PNC formation and myocardial reperfusion injury. Given the clinical importance of hepatic IR injury we pursued the role of VASP during hepatic ischemia followed by reperfusion. We report here that VASP^−/− animals demonstrate reduced hepatic IR injury compared to wildtype (WT) controls. This correlated with serum levels of lactate dehydrogenase (LDH), aspartate (AST) and alanine (ALT) aminotransferase and the presence of PNCs within ischemic hepatic tissue and could be confirmed using repression of VASP through siRNA. In studies employing bone marrow chimeric mice we identified hematopoietic VASP to be of crucial importance for the extent of hepatic injury. Phosphorylation of VASP on Ser¹⁵³ through Prostaglandin E1 or on Ser²³⁵ through atrial natriuretic peptide resulted in a significant reduction of hepatic IR injury. This was associated with a reduced presence of PNCs in ischemic hepatic tissue. Taken together, these studies identified VASP and VASP phosphorylation as crucial target for future hepatoprotective strategies.

Serum N-terminal pro-B-type natriuretic peptide levels are associated with functional capacity in patients with peripheral arterial disease

We hypothesized that higher serum levels of N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) are associated with lower functional capacity in patients with peripheral arterial disease ([PAD] n = 481, mean age 67, 68% men). Functional capacity was quantified as distance walked on a treadmill for 5 minutes. Patients were divided into 3 groups according to the distance walked: >144 yards (group 1, n = 254); 60 to 144 yards (group 2, n = 80); <60 yards or did not walk (group 3, n = 147). The association between NT-pro-BNP levels and the ordinal 3-level walking distance was assessed using multivariable ordinal logistic regression analyses that adjusted for several possible confounding variables. Higher levels of NT-pro-BNP were associated with a lower ordinal walking category independent of possible confounders (odds ratio [OR] 1.51, 95% confidence interval [CI] 1.28-1.77; P < .001). In conclusion, higher levels of NT-pro-BNP are independently associated with lower functional capacity in patients with PAD and may be a marker of hemodynamic stress in these patients.

Nitric oxide and P-glycoprotein modulate the phagocytosis of colon cancer cells

The anticancer drug doxorubicin induces the synthesis of nitric oxide, a small molecule that enhances the drug cytotoxicity and reduces the drug efflux through the membrane pump P-glycoprotein (Pgp). Doxorubicin also induces the translocation on the plasma membrane of the protein calreticulin (CRT), which allows tumour cells to be phagocytized by dendritic cells. We have shown that doxorubicin elicits nitric oxide synthesis and CRT exposure only in drug-sensitive cells, not in drug-resistant ones, which are indeed chemo-immunoresistant. In this work, we investigate the mechanisms by which nitric oxide induces the translocation of CRT and the molecular basis of this chemo-immunoresistance. In the drug-sensitive colon cancer HT29 cells doxorubicin increased nitric oxide synthesis, CRT exposure and cells phagocytosis. Nitric oxide promoted the translocation of CRT in a guanosine monophosphate (cGMP) and actin cytoskeleton-dependent way. CRT translocation did not occur in drug-resistant HT29-dx cells, where the doxorubicin-induced nitric oxide synthesis was absent. By increasing nitric oxide with stimuli other than doxorubicin, the CRT exposure was obtained also in HT29-dx cells. Although in sensitive cells the CRT translocation was followed by the phagocytosis, in drug-resistant cells the phagocytosis did not occur despite the CRT exposure. In HT29-dx cells CRT was bound to Pgp and only by silencing the latter the CRT-operated phagocytosis was restored, suggesting that Pgp impairs the functional activity of CRT and the tumour cells phagocytosis. Our work suggests that the levels of nitric oxide and Pgp critically modulate the recognition of the tumour cells by dendritic cells, and proposes a new potential therapeutic approach against chemo-immunoresistant tumours.

IRAG and novel PKG targeting in the cardiovascular system

Signaling by nitric oxide (NO) determines several cardiovascular functions including blood pressure regulation, cardiac and smooth muscle hypertrophy, and platelet function. NO stimulates the synthesis of cGMP by soluble guanylyl cyclases and thereby activates cGMP-dependent protein kinases (PKGs), mediating most of the cGMP functions. Hence, an elucidation of the PKG signaling cascade is essential for the understanding of the (patho)physiological aspects of NO. Several PKG signaling pathways were identified, meanwhile regulating the intracellular calcium concentration, mediating calcium desensitization or cytoskeletal rearrangement. During the last decade it emerged that the inositol trisphosphate receptor-associated cGMP-kinase substrate (IRAG), an endoplasmic reticulum-anchored 125-kDa membrane protein, is a main signal transducer of PKG activity in the cardiovascular system. IRAG interacts specifically in a trimeric complex with the PKG1β isoform and the inositol 1,4,5-trisphosphate receptor I and, upon phosphorylation, reduces the intracellular calcium release from the intracellular stores. IRAG motifs for phosphorylation and for targeting to PKG1β and 1,4,5-trisphosphate receptor I were identified by several approaches. The (patho)physiological functions for the regulation of smooth muscle contractility and the inhibition of platelet activation were perceived. In this review, the IRAG recognition, targeting, and function are summarized compared with PKG and several PKG substrates in the cardiovascular system.

Essential roles of the nitric oxide (no)/cGMP/protein kinase G type-Iα (PKG-Iα) signaling pathway and the atrial natriuretic peptide (ANP)/cGMP/PKG-Iα autocrine loop in promoting proliferation and cell survival of OP9 bone marrow stromal cells

Inappropriate signaling conditions within bone marrow stromal cells (BMSCs) can lead to loss of BMSC survival, contributing to the loss of a proper micro-environmental niche for hematopoietic stem cells (HSCs), ultimately causing bone marrow failure. In the present study, we investigated the novel role of endogenous atrial natriuretic peptide (ANP) and the nitric oxide (NO)/cGMP/protein kinase G type-Iα (PKG-Iα) signaling pathway in regulating BMSC survival and proliferation, using the OP9 BMSC cell line commonly used for facilitating the differentiation of HSCs. Using an ANP-receptor blocker, endogenously produced ANP was found to promote cell proliferation and prevent apoptosis. NO donor SNAP (S-nitroso-N-acetylpenicillamine) at low concentrations (10 and 50 µM), which would moderately stimulate PKG activity, protected these BMSCs against spontaneous apoptosis. YC-1, a soluble guanylyl cyclase (sGC) activator, decreased the levels of apoptosis, similar to the cytoprotective effects of low-level NO. ODQ (1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one), which blocks endogenous NO-induced activation of sGC and thus lowers endogenous cGMP/PKG activity, significantly elevated apoptotic levels by 2.5- and three-fold. Pre-incubation with 8-Bromo-cGMP or ANP, which bypass the ODQ block, almost completely prevented the ODQ-induced apoptosis. A highly-specific PKG inhibitor, DT-3, at 20, and 30 µM, caused 1.5- and two-fold increases in apoptosis, respectively. ODQ and DT-3 also decreased BMSCs proliferation and colony formation. Small Interfering RNA gene knockdown of PKG-Iα increased apoptosis and decreased proliferation in BMSCs. The data suggest that basal NO/cGMP/PKG-Iα activity and autocrine ANP/cGMP/PKG-Iα are necessary for preserving OP9 cell survival and promoting cell proliferation and migration.

Nitric oxide stimulates human neural progenitor cell migration via cGMP-mediated signal transduction

Neuronal migration is one of the most critical processes during early brain development. The gaseous messenger nitric oxide (NO) has been shown to modulate neuronal and glial migration in various experimental models. Here, we analyze a potential role for NO signaling in the migration of fetal human neural progenitor cells. Cells migrate out of cultured neurospheres and differentiate into both neuronal and glial cells. The neurosphere cultures express neuronal nitric oxide synthase and soluble guanylyl cyclase that produces cGMP upon activation with NO. By employing small bioactive enzyme activators and inhibitors in both gain and loss of function experiments, we show NO/cGMP signaling as a positive regulator of migration in neurosphere cultures of early developing human brain cells. Since NO signaling regulates cell movements from developing insects to mammalian nervous systems, this transduction pathway may have evolutionary conserved functions.

Phosphorylation of vasodilator-stimulated phosphoprotein prevents platelet-neutrophil complex formation and dampens myocardial ischemia-reperfusion injury

BACKGROUND

Recent work has suggested that the formation of platelet-neutrophil complexes (PNCs) aggravates the severity of inflammatory tissue injury. Given the importance of vasodilator-stimulated phosphoprotein (VASP) for platelet function, we pursued the role of VASP on the formation of PNCs and its impact on the extent of myocardial ischemia-reperfusion (IR) injury.

METHODS AND RESULTS

In initial in vitro studies we found that neutrophils facilitated the movement of platelets across endothelial monolayers. Phosphorylation of VASP reduced the formation of PNCs and transendothelial movement of PNCs. During myocardial IR injury, VASP(-/-) animals demonstrated reduced intravascular formation of PNCs and reduced presence of PNCs within the ischemic myocardial tissue. This was associated with reduced IR injury. Studies using platelet transfer and bone marrow chimeric animals showed that hematopoietic VASP expression was crucial for the intravascular formation of PNCs the presence of PNCs within ischemic myocardial tissue and the extent of myocardial IR injury. Furthermore, phosphorylation of VASP on Ser153 or Ser235 reduced intravascular PNC formation and presence of PNCs within ischemic myocardial tissue. This finding was associated with reduced myocardial IR injury.

CONCLUSION

Previously unappreciated, the phosphorylation of VASP performs a key function for the formation of PNCs that is crucially important for the extent of myocardial IR injury.

SNO-ing at the nociceptive synapse?

Nitric oxide is generally considered a pronociceptive retrograde transmitter that, by activation of soluble guanylyl cyclase-mediated cGMP production and activation of cGMP-dependent protein kinase, drives nociceptive hypersensitivity. The duality of its functions, however, is increasingly recognized. This review summarizes nitric-oxide-mediated direct S-nitrosylation of target proteins that may modify nociceptive signaling, including glutamate receptors and G-protein-coupled receptors, transient receptor potential channels, voltage-gated channels, proinflammatory enzymes, transcription factors, and redoxins. S-Nitrosylation events require close proximity of nitric oxide production and target proteins and a permissive redox state in the vicinity. Despite the diversity of potential targets and effects, three major schemes arise that may affect nociceptive signaling: 1) S-Nitrosylation-mediated changes of ion channel gating properties, 2) modulation of membrane fusion and fission, and thereby receptor and channel membrane insertion, and 3) modulation of ubiquitination, and thereby protein degradation or transcriptional activity. In addition, S-Nitrosylation may alter the production of nitric oxide itself.